WordPress MU and Buddypress have separate profile/user management tables that aren’t synchronized and in some ways clash. End users will see different profile editing screens, in wp-admin and buddypress front-end, with different data that have nothing to do with eachother. Users are identified by full name, username, nickname, blogname or whatever depending on where in the system you are and how it’s configured. It’s a confusing mess and my pet peeve.

But I’m not even sure if that’s relevant to your problem, so I removed the rant.

I also just noticed that buddypress profiles don’t import from wordpress profiles or vice versa. It takes enough tooth pulling to get people to complete one profile. Adding those fields to sign up would be good because required fields would also have some anti-spam benefits.